head to head
Portal asks more than Bloons TD 6, and the gap is execution.

Optimization · Pure Optimization
A deep tower defense about popping waves of balloons with monkey towers.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Bloons TD 6 leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Bloons TD 6
Placement clicks only; no dexterity ceiling
Portal
Portal placement timing modest.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Bloons TD 6
Bloon waves are fixed and known
Portal
No adversary modeling player.
Bloons TD 6 leans a little harder on variance, though the gap is small.
Bloons TD 6
Wave order is deterministic; tiny targeting randomness
Portal
Deterministic chambers; no randomness.
Bloons TD 6 leans a little harder on optimization, though the gap is small.
Bloons TD 6
Tower placement, upgrades, and economy are near-solvable
Portal
Pure puzzle-solving optimization.
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.